Parking assistance device and parking assistance method

ABSTRACT

A parking assistance device is applied to a vehicle equipped with a camera for capturing an image of an area in front of the vehicle and is configured to assist forward parking of the vehicle in a parking space. The parking assistance device includes: a position estimation unit which, in a situation where the vehicle is advancing toward the parking space in a lateral passage of the parking space, estimates, based on an image captured by the camera, at least one of a first corner position, which is a near-side corner position at a vehicle entrance part of the parking space, and a second corner position, which is a far-side corner position at the vehicle entrance part, before the vehicle passes by the parking space; and a space recognition unit which recognizes the parking space for forward parking based on the at least one estimated corner position.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a national stage application of PCTApplication No. PCT/JP2017/019617, filed on May 25, 2017, which is basedon Japanese Application No. 2016-107623 filed on May 30, 2016, thecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a parking assistance device and aparking assistance method, and in particular, to a parking assistancedevice and a parking assistance method applied to a vehicle equippedwith a camera that captures an image of an area in front of the vehicle.

BACKGROUND ART

A conventional, known parking assistance device uses a ranging sensor oran in-vehicle camera to recognize the environment around the vehicle,and recognizes the parking space or calculates the parking route basedon the recognition result (see, for example, PTL 1). The parkingassistance device of PTL 1 detects the empty space of a parking spaceformed in a parking lot and predicts a plurality of patterns of leavingroute for leaving from the detected empty space. In addition, it isdisclosed that a leaving route is selected from the plurality ofpatterns based on their difficulty levels, and guidance of a forward orreverse parking method is given as the parking method for leaving in theselected leaving route.

CITATION LIST Patent Literature

[PTL 1] JP 2007-320433 A

SUMMARY OF THE INVENTION

The forward parking, i.e., parking by making the vehicle enter theparking space forwards, requires a shorter route for parking as comparedwith the reverse parking, i.e., parking by making the vehicle enter inreverse. On the other hand, in the case of forward parking, since thevehicle directly enters the parking space from a lateral passage infront of the parking space, it is necessary to start the steering beforereaching the parking space. At this time, if the recognition of theparking space is delayed, the start of steering to enter the parkingspace is delayed, and as a result the driver must repeatedly steer thevehicle and move the vehicle back and forth to park the vehicle.

The present disclosure has been made in view of the above points, and anobject thereof is to provide a parking assistance device and a parkingassistance method capable of recognizing a parking space at an earlystage and smoothly performing forward parking to the parking space.

In order to solve the above points, the present disclosure adopts thefollowing means.

A first aspect of the present disclosure relates to a parking assistancedevice applied to a vehicle equipped with a camera for capturing animage of an area in front of the vehicle and configured to assistforward parking of the vehicle in a parking space. The parkingassistance device comprises: a position estimation unit which, in asituation where the vehicle is advancing toward the parking space in alateral passage of the parking space, estimates, based on an imagecaptured by the camera, at least one of a first corner position, whichis a near-side corner position at a vehicle entrance part of the parkingspace, and a second corner position, which is a far-side corner positionat the vehicle entrance part, before the vehicle passes by the parkingspace; and a space recognition unit which recognizes the parking spacefor forward parking based on the at least one corner position estimatedby the position estimation unit.

According to the above configuration, the corner positions of theentrance part of the parking space in which the vehicle should be parkedforward are estimated before the vehicle passes by the parking space,based on an image of an area in front of the vehicle captured by thecamera. According to this configuration, since the parking space can bedetected at an earlier stage before the vehicle passes by the parkingspace, the process required for forward parking the vehicle in theparking space can be started earlier. Therefore, according to the aboveconfiguration, forward parking in the parking space can be performedsmoothly.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the presentdisclosure will become clearer from the following detailed descriptionwith reference to the accompanying drawings. In the drawings,

FIG. 1 is a block diagram showing the general configuration of theparking assistance system.

FIG. 2 is a diagram showing the installation position of the rangingsensor.

FIG. 3 is a diagram showing a case where forward parking is performedusing the second corner position obtained from the detected distance ofthe ranging sensor.

FIG. 4 is a diagram showing a case where forward parking is performedusing the second corner position estimated from the captured image.

FIG. 5 is a flowchart showing the procedures of the parking assistanceprocess.

FIG. 6 is a diagram for explaining the way of estimating the firstcorner position using the captured image.

FIG. 7 is a flowchart showing the procedures of the parking assistanceprocess of the second embodiment.

FIG. 8 is a flowchart showing the procedures of the parking assistanceprocess of another embodiment.

DESCRIPTION OF THE EMBODIMENTS First Embodiment

The first embodiment will be described below with reference to thedrawings. The same or equivalent parts in the embodiments describedbelow are assigned with the same reference number in the drawings, andan earlier explanation should be referred to regarding those partshaving the same reference number as another.

First, a parking assistance system of this embodiment will be describedwith reference to FIGS. 1 and 2. The parking assistance system of thisembodiment is mounted on a vehicle (hereinafter referred to as “ownvehicle”). As shown in FIG. 1, the parking assistance system includes anin-vehicle camera 21, a ranging sensor 22, and a parking assistancedevice 10.

The in-vehicle camera 21 comprises, for example, a CCD camera, a CMOSimage sensor, a near infrared camera, or the like. The in-vehicle camera21 is attached to a front part of the vehicle 40, at the center of thevehicle width and at a certain height (for example, above the frontbumper), and it captures an image of an area spreading at apredetermined angle in front of the vehicle in the bird's eye view. Thein-vehicle camera 21 may be a monocular camera or a stereo camera.

The ranging sensor 22 is a sensor that detects the distance to anobstacle existing near the own vehicle 40. In the present embodiment,the ranging sensor 22 transmits a probe wave at certain controlintervals, and receives the reflected wave reflected by the obstacleexisting near the own vehicle 40. The distance from the own vehicle 40to the obstacle existing near the own vehicle 40 is calculated based onround-trip time which is the time from transmission to reception. Theranging sensor 22 may be, for example, an ultrasonic sensor such as asonar sensor. It should be noted that the ranging sensor 22 is notlimited to an ultrasonic sensor, but may be a sensor such as a lasersensor, a millimeter wave sensor, or the like.

FIG. 2 is a diagram showing the installment position of the rangingsensor 22 in the own vehicle 40. The ranging sensor 22 is installed at aplurality of locations of the own vehicle 40. In the present embodiment,as shown in FIG. 2, a plurality of ranging sensors 22 having differentdetection areas are attached to the own vehicle 40 at certain intervalsat the front bumper part, the rear bumper part, and the sides of thevehicle body.

Specifically, the ranging sensors 22 include center sensors 26 attachednear the center axis 41 of the vehicle width and symmetrically withrespect to the center axis 41, corner sensors 27 attached to the leftcorner and the right corner of the own vehicle 40, and lateral sensors28 attached to the left side and the right side of the own vehicle 40.The center sensors 26 have detection areas 92 and 93 extending in frontof the vehicle, the corner sensors 27 have detection areas 94 and 95extending obliquely from the vehicle, and the lateral sensors 28 havedetection areas 96 and 97 extending laterally from the vehicle. Thereference number 91 represents an imaging area of the in-vehicle camera21. As shown in FIG. 2, the in-vehicle camera 21 is capable of capturingan image of an area extending further than the detection areas of theranging sensors 22.

In addition to the in-vehicle camera 21 and the ranging sensors 22various sensors, switches, and the like are provided in the own vehicle40 such as a vehicle speed sensor 23 for detecting the vehicle speed, asteering angle sensor 24 for detecting the steering angle, and a forwardparking switch 25 for allowing the driver to command automatic parkingby forward parking.

The parking assistance device 10 is a computer comprising a CPU, ROM,RAM, I/O, and the like, and it realizes various functions to performparking assistance of the own vehicle 40 by executing programs installedin the ROM with the CPU. The ROM corresponds to a computer-readablestorage medium serving as a non-transitory tangible storage medium. Theparking assistance device 10 receives various kinds of information fromthe various sensors and switches provided in the own vehicle 40 andperforms processing for recognizing a parking space existing around theown vehicle 40 based on the received various kinds of information.Further, the parking assistance device 10 calculates a parking route forautomatically parking the own vehicle 40 to the recognized parkingspace, and controls a steering device 31, a drive-force device 32, and abraking device 33 of the own vehicle 40 so as to automatically park theown vehicle 40 according to the calculated parking route.

In the case of forward parking, when the own vehicle 40 is travelingtoward the parking space in a lateral passage which is located near theentrance of the parking space, the parking assistance device 10calculates a first corner position which is the corner position of theparking space that is closer to the vehicle, and a second cornerposition which is the corner position that is further from the vehicle,and recognizes the space between the first corner position and thesecond corner position as the parking space. The first corner positionis also a corner position of the obstacle adjacent to the parking spacethat is closer to the vehicle (hereinafter also referred to as the “nearside obstacle”), and the second corner position is also a cornerposition of the obstacle adjacent to the parking space that is furtherfrom the vehicle (hereinafter also referred to as the “far sideobstacle”). The corner positions may be calculated by, for example,detecting the contour points of the near side obstacle and the far sideobstacle based on the distance information acquired by the rangingsensor 22, and determining the corner positions based on the detectionhistory of the contour points.

When the ranging sensor 22 is a sensor that transmits a probe wave andreceives the reflected wave reflected by an obstacle, the reflectionpoints on the obstacle of the probe waves transmitted from the rangingsensor 22 will be the contour points. In this case, a sequence of thereflection points is obtained, and the end point of the sequence, or apoint offset by a predetermined distance from the end point of thesequence is identified as the corner position. The reflection points ofthe obstacle may be calculated by, for example, calculating the sensorposition for each obstacle detection based on the vehicle speed detectedby the vehicle speed sensor 23 and the steering angle detected by thesteering angle sensor 24, and calculating the reflection points by theprinciple of triangulation based on based on the history of the obtainedsensor positions and the history of the information on the distance tothe obstacle.

In the case of forward parking, if the corner position of the far sideobstacle adjacent to the parking space, that is, the second cornerposition is to be detected by the ranging sensor 22, the own vehicle 40is required to once pass by the parking space, move backward afterrecognizing the far side environment of the parking space, and thencalculate the route for automatic forward parking.

FIG. 3 is a diagram showing a route of the own vehicle 40 when it isgoing to be automatically parked to the parking space 50 by forwardparking by detecting the first corner position and the second cornerposition with the ranging sensor 22. In FIG. 3, it is assumed that theown vehicle 40 is parked forward from a lateral passage 51 in front ofthe parking space 50 that is sandwiched between two parallelly parkedvehicles 61 and 62. The parked vehicle 61 corresponds to the near sideobstacle, and the parked vehicle 62 corresponds to the far sideobstacle.

In FIG. 3(a), as the own vehicle 40 passes by the parked vehicle 61which is the near side obstacle, the distance to the parked vehicle 61is successively detected by the ranging sensor 22 (mainly by the lateralsensor 28). As a result, the sequence of the reflection points 70 on theparked vehicle 61 is obtained. Based on this sequence, a far-side cornerpoint 63 of the parked vehicle 61 is calculated as the first cornerposition. After that, the own vehicle 40 once passes in front theparking space 50 and travels to the front of the parked vehicle 62 whichis the far side obstacle adjacent to the parking space 50. As a result,the sequence of the reflection points 71 on the parked vehicle 62 isobtained by the ranging sensor 22, and based on this sequence, anear-side corner point 64 of the parked vehicle 62 is calculated as thesecond corner position. Note that the “near-side corner point” the oneof the corner positions (corner points) of an obstacle adjacent to theparking space 50 that is located closer to the own vehicle 40 when it ismoving toward the parking space 50, and the “far-side corner point” isthe corner point located further from the vehicle.

After that, as shown in FIG. 3(b), after the own vehicle 40 has passedby the parking space 50 and reversed to the vicinity of the parkedvehicle 61, forward parking is performed toward the parking space 50which has been recognized from the first corner position and the secondcorner position detected by the ranging sensor 22. However, when such amethod is applied, the route for the forward parking to the parkingspace 50 becomes long, and this may cause a time loss.

In view of such matters, the present embodiment estimates the cornerpositions of the parking space 50 based on the image captured by thein-vehicle camera 21, and recognizes the parking space 50 for forwardparking using the estimated corner positions. In particular, the presentembodiment calculates the first corner position based on the distanceinformation acquired by the ranging sensor 22, and estimates the secondcorner position based on the image captured by the in-vehicle camera 21.

FIG. 4 is a diagram showing the route of the own vehicle 40 in the caseit is parked forward using the image captured by the in-vehicle camera21. In FIG. 4, as with FIG. 3, it is assumed that the own vehicle 40 isparked forward from the lateral passage 51 in the front of the parkingspace 50 that is sandwiched between two parallelly parked vehicles 61and 62.

In FIG. 4(a), when the own vehicle 40 passes by the parked vehicle 61 onthe near side of the parking space 50, the parking assistance device 10calculates the far-side corner point 63 of the parked vehicle 61 as thefirst corner position from the sequence of the reflection points 70 onthe parked vehicle 61 detected by the ranging sensor 22. Further, byobtaining from the image the position information of the parked vehicle62 which is the far-side obstacle, the near-side corner point 64 of theparked vehicle 62 on the far side is estimated as the second cornerposition. After recognizing the parking space 50 from the first cornerposition and the second corner position thus determined, as shown inFIG. 4(b), automatic parking is performed for forward parking toward therecognized parking space 50. According to this method, since the parkingspace 50 can be recognized when the own vehicle 40 passes by thenear-side obstacle, the need for preparing a route for recognizing theparking space 50 is eliminated. In addition, since the parking space 50can be recognized when the vehicle passes by the near-side obstacle,steering can be performed earlier. Thus, it is possible to park thevehicle directly in the parking space 50 without turning the steeringwheel a plurality of times.

As a configuration for performing forward parking as described above, asshown in FIG. 1, the parking assistance device 10 includes a cornerposition calculation unit 11, a parking space recognition unit 12, and aroute calculation unit 13.

The corner position calculation unit 11 inputs the captured image of thein-vehicle camera 21 and the detected distance of the ranging sensor 22.Further, it calculates the first corner position of the parking space 50using the input detected distance of the ranging sensor 22, andestimates the second corner position using the captured image of thein-vehicle camera 21. The corner position calculation unit 11 functionsas the “position estimation unit” and the “position detection unit”.

Speaking more specifically about the estimation of the second cornerposition based on the image, the corner position calculation unit 11first extracts edge points as feature points indicating the presence ofa target in the captured image in order to detect the boundary edge ofthe far-side obstacle (the parked vehicle 62 in FIG. 4) of the parkingspace 50. Further, based on the detected boundary edge, it estimates anarea in which the far-side obstacle exists, and based on the estimatedexistence area and the distance information of the target with respectto the own vehicle 40 obtained from the image, it estimates the cornerposition of the far-side obstacle that is closer to the parking space50, that is, the near-side corner point 64 of the parked vehicle 62.FIG. 4 shows edge points 80 of the parked vehicle 62 extracted from thecaptured image and converted for a bird's-eye view. Based on the surfaceinformation of the obstacle obtained from the edge points 80, the cornerposition of the obstacle closer to the parking space 50, that is, thesecond corner position is estimated.

Note that the way of detecting an obstacle adjacent to the parking space50 using the in-vehicle camera 21 is not particularly limited. Forexample, it may be performed by three-dimensional object detection basedon parallax information obtained from a plurality of images taken fromdifferent positions. When the in-vehicle camera 21 is a monocularcamera, it is carried out according to the principle of derivingparallax from sequential images. In addition, the obstacle detection bythe in-vehicle camera 21 may identify the type of the target recognizedby the in-vehicle camera 21 by performing pattern matching on the imagetarget using predetermined patterns.

In estimating the second corner position, the distance information ofthe target with respect to the own vehicle 40 on the image is acquiredbased on disparity information obtained from a plurality of imagescaptured from different positions. For example, when the in-vehiclecamera 21 is a stereo camera, parallax information is acquired for eachpixel from images captured simultaneously by a plurality of cameras, anddistance information of the target is acquired using the parallaxinformation. When the in-vehicle camera 21 is a monocular camera, it iscarried out according to the principle of deriving parallax fromsequential images. Specifically, parallax information is acquired foreach pixel from a plurality of frames captured at different timings andthe movement distances between frames, and distance information of thetarget is acquired using the parallax information.

The parking space recognition unit 12 inputs the position information ofthe first corner position and the second corner position acquired by thecorner position calculation unit 11, and sets the space between thefirst corner position and the second corner position as the parkingspace 50. At this time, it is also possible to determine whether or notthe own vehicle 40 can be parked in the space based on the width of thespace between the first corner position and the second corner positionand the vehicle width of the own vehicle 40, and set the space as theparking space 50 when it is determined that parking is possible.

The route calculation unit 13 calculates a route for forward parking theown vehicle 40 in the parking space 50 recognized by the parking spacerecognition unit 12. The steering device 31, the drive-force device 32,and the braking device 33 are controlled by the parking assistancedevice 10 so that the own vehicle 40 is automatically parked forward inthe parking space 50 following the route thus calculated.

Next, the parking assistance process executed by the parking assistancedevice 10 of the present embodiment will be described with reference tothe flowchart of FIG. 5. This process is executed by the CPU of theparking assistance device 10 when an ON signal is input from the forwardparking switch 25.

In FIG. 5, in step S11, using the distance information acquired by theranging sensor 22, the sequence of the reflection points on thenear-side obstacle is detected, and the first corner position isidentified from the sequence. In step S12, the position information ofthe far-side obstacle (62) is acquired from an image taken before thevehicle passes by the parking space 50, and the second corner positionis estimated. In the following step S13, the space between the firstcorner position and the second corner position is recognized as theparking space 50. After that, in step S14, a route for forward parkingthe own vehicle 40 in the parking space 50 is calculated. In step S15,actuation commands are output to the steering device 31, the drive-forcedevice 32, and the braking device 33 so that the forward parking isautomatically performed based on the calculated route, and then thepresent process is terminated.

According to the present embodiment described above, the followingadvantageous effects can be obtained.

The corner positions of a vehicle entrance part 52 of the parking space50 in which the own vehicle 40 should be parked forward are estimatedbefore the own vehicle 40 passes by the parking space 50, based on animage of an area in front of the vehicle captured by the in-vehiclecamera 21. According to this configuration, since the parking space 50can be detected before the own vehicle 40 passes by the parking space50, the process required for forward parking the vehicle in the parkingspace 50, specifically, the process including steering, routecalculation, and the like can be started earlier. Therefore, forwardparking in the parking space 50 can be performed smoothly.

The position information of the far-side obstacle of the parking space50 is acquired from an image taken by the in-vehicle camera 21 beforethe vehicle passes by the parking space 50, in order to estimate thesecond corner position. More specifically, by extracting edge points ofthe far-side obstacle of the parking space 50 from the image, theexistence area of the second corner position is estimated, and thesecond corner position is estimated based on the estimated existencearea and distance information of the far-side obstacle acquired from theimage. If the second corner position is to be determined using theranging sensor 22, the own vehicle 40 needs to pass by the parking space50 once and advance to the far-side obstacle located beyond the parkingspace 50. In this respect, according to the configuration thatdetermines that corner position, which is in the area not suitable fordetection by the ranging sensor 22, from the image of the in-vehiclecamera 21, it is possible to obtain the second corner position beforepassing by the parking space 50 without disadvantageously advancing theown vehicle 40 to the far-side obstacle located beyond the parking space50.

The first corner position is detected based on the detection history ofcontour points of the near-side obstacle detected by the ranging sensor22, and the space between the detected first corner position and thesecond corner position estimated using the captured image is recognizedas the parking space 50. According to this configuration, in a situationwhere the own vehicle 40 is advancing toward the parking space 50, anobstacle on the near side of the parking space 50 is recognized by theranging sensor 22, whereas the obstacle on the far side of the parkingspace 50 can be recognized by the in-vehicle camera 21. In addition,since the first corner position is detected using the ranging sensor 22having a higher detection accuracy for three-dimensional objects, thedetection accuracy is higher. Therefore, according to the aboveconfiguration, it is possible to achieve both recognition of the parkingspace at an earlier stage and high recognition accuracy.

The above technique is applied to a system that performs automaticparking control which parks the own vehicle 40 automatically in theparking space 50 by forward parking based on the recognition result ofthe parking space 50. According to the method of recognizing the parkingspace 50 of the present disclosure, since the parking space 50 can berecognized while the own vehicle 40 is advancing toward the parkingspace 50, by combining this with automatic parking control, the ownvehicle 40 can be smoothly forward parked in the parking space 50.

Second Embodiment

The second embodiment will now be explained focusing on its differencesfrom the first embodiment. In the first embodiment, in order torecognize the parking space 50, the first corner position is identifiedusing the distance information acquired by the ranging sensor, and thesecond corner position is estimated using the captured image. On theother hand, in the present embodiment, the parking space 50 isrecognized by estimating the first corner position and the second cornerposition using the captured image.

FIG. 6 is a diagram for explaining the way of estimating the firstcorner position using the captured image. Since the second cornerposition is estimated in the same manner as in the first embodiment, thedescription thereof will be omitted. In FIG. 6, as with FIG. 4, it isassumed that the own vehicle 40 is parked forward from the lateralpassage 51 in front of the parking space 50 that is sandwiched betweentwo parallelly parked vehicles 61 and 62. However, in FIG. 6, it isassumed that the own vehicle 40 has not approached the parking space 50so much, and the first corner position is not yet detected by theranging sensor 22.

In FIG. 6, the near-side corner point 65, which is the one of the cornerpositions of the parked vehicle 61 as the near-side obstacle that is onthe side opposite to the parking space 50 and on the side of the lateralpassage 51, is already detected based on the sequence of the reflectionpoints 70 of the ranging sensor 22, but the far-side corner point 63 asthe first corner position is not. In such a case, in the presentembodiment, based on the image captured by the in-vehicle camera 21, aposition obtained by offsetting the near-side corner point 65 of theparked vehicle 61 by a predetermined amount in the direction in whichthe own vehicle 40 advances toward the parking space 50 is estimated asthe first corner position. In other words, based on the near-side cornerpoint 65 of the parked vehicle 61 detected by the ranging sensor 22 andthe symmetry of the parked vehicle 61 detected by the in-vehicle camera21, the first corner position which is the far-side corner point 63 ofthe parked vehicle 61 is estimated.

More specifically, when the vehicle is to be parked parallelly withparked vehicles 61 and 62, the corner position calculating unit 11extracts a feature(s) (for example, the front grille, lamps, licenseplate, door mirror, etc.) indicating the symmetry of the own vehicle 40in the vehicle width direction from the image captured by the in-vehiclecamera 21 by, for example, pattern matching or the like. According tothe extracted feature, a vehicle center axis 66 of the parked vehicle 61is estimated. Then, the near-side corner point 65 detected by theranging sensor 22 is mirror-inverted with respect to the estimatedvehicle center axis 66, and the obtained position is estimated as thefar-side corner point 63, that is, the first corner position. Thenear-side corner point 65 of the parked vehicle 61 corresponds to athird corner position.

Next, the parking assistance process executed by the parking assistancedevice 10 of the present embodiment will be described with reference tothe flowchart of FIG. 7. This process is executed by the CPU of theparking assistance device 10 when an ON signal is input from the forwardparking switch 25. In the description of FIG. 7, the steps that are thesame as those in FIG. 5 are given the step numbers in FIG. 5 and thedescription thereof is omitted.

In FIG. 7, in step S21, the first corner position and the second cornerposition are estimated using the captured image. At this time, the firstcorner position is estimated based on the near-side corner point 65 ofthe parked vehicle 61 detected by the ranging sensor 22 and the symmetryof the parked vehicle 61 detected by the in-vehicle camera 21. Thesecond corner position is estimated by acquiring the positioninformation of the far-side obstacle of the parking space 50 from animage taken by the in-vehicle camera 21. In the following steps S22 toS24, the same processing as the steps S13 to S15 in FIG. 5 is executed,and the present cycle ends.

According to the present embodiment described above, since the parkingspace 50 is recognized by estimating the first corner position and thesecond corner position using the captured image, it is possible torecognize the parking space 50 for forward parking at an earlier stage.

The third corner position is detected based on the detection history ofcontour points of the near-side obstacle detected by the ranging sensor22, and a position obtained by, based on the image captured by thein-vehicle camera 21 offsetting the detected third corner position by apredetermined amount in the direction in which the own vehicle 40advances toward the parking space 50 is estimated as the first cornerposition. According to such a configuration, it is possible to obtainthe first corner position before the first corner position is detectedby the ranging sensor 22, that is, at an earlier stage while the ownvehicle 40 is passing by the near-side obstacle. As a result, it ispossible to recognize the parking space 50 for forward parking at anearlier stage.

Other Embodiments

The present disclosure is not limited to the above embodiments, and itmay be implemented as follows, for example.

In the above embodiments, if the second corner position is detected bythe ranging sensor 22, and the second corner position estimated based onthe image and the second corner position detected by the ranging sensor22 are within a predetermined area in which they can be deemed to belocated at the same position, the estimation reliability of the secondcorner position by the image may be made higher than when the secondcorner position is not detected by the ranging sensor 22. In some cases,for example, the corner sensor 27 may be able to detect the secondcorner position before the own vehicle 40 passes by the parking space50. In such a case, it can be said that it is more likely that thesecond corner position estimated using the captured image exists at theestimated position. In view of this point, by adopting the aboveconfiguration, parking assistance can be performed in a manner accordingto the estimation reliability of the second corner position.Specifically, for example, when the estimation reliability of the secondcorner position is high, the forward parking is performed at a higherspeed. Alternatively, when the estimation reliability of the secondcorner position is high, a route having a higher difficulty may becalculated, and when the estimation reliability of the second cornerposition is low, forward parking may be performed with a safer route.

FIG. 8 is a flowchart showing the procedures of the parking assistanceprocess in which the estimation reliability of the second cornerposition is changed based on the detection result of the ranging sensor22. In the description of FIG. 8, the steps that are the same as thosein FIG. 5 are given the step numbers in FIG. 5 and the descriptionthereof is omitted. In FIG. 8, in steps S31 to S32, the same processingas the steps S11 to S12 in FIG. 5 is executed. In the following stepS33, it is determined whether or not the second corner position isdetected by the ranging sensor 22. Here, it is determined whether or nota sequence of the reflection points of the far-side obstacle isdetected. If the second corner position is not detected by the rangingsensor 22, the process proceeds to step S34, and the estimationreliability of the second corner position according to the image is setto “A”. On the other hand, if the second corner position is detected bythe ranging sensor 22, the process proceeds to step S35, and theestimation reliability of the second corner position according to theimage is set to “B” which is higher than “A”. In the following step S36,the parking space 50 is recognized based on the first corner positionand the second corner position. Further, in step S37, a parking routefor forward parking is calculated according to the estimationreliability. At this time, when the estimation reliability of the secondcorner position is A, a route that is safer than that in the case of Bis chosen. After that, the process ends.

In the above embodiments, the parking route for forward parking may becalculated based on whether or not presence of a far-side obstacleadjacent to the parking space 50 is detected according to the capturedimage of the in-vehicle camera 21. For example, when it is detected thatthere is no far-side obstacle, as compared with when a far-side obstacleis detected, a route with a higher reliability of one-time forwardparking is calculated.

In the above embodiments, when it is detected that there is no far-sideobstacle adjacent to the parking space 50, and a marking line isrecognized on the far side of the parking space 50 by the in-vehiclecamera 21, the parking space 50 may be corrected based on theinformation on the position and orientation of the near-side obstacle.For example, based on the sequence of the reflection points 70 of thenear-side obstacle detected by the ranging sensor 22, the offset of thenear-side obstacle in the direction toward the parking space 50 and theorientation of the near-side obstacle with respect to the parking space50 are recognized, and the parking space 50 is corrected based on therecognized information.

The position of the estimated existence area of the second cornerposition based on the edge points of the far-side obstacle may bechanged according to the orientation of the far-side obstacle. Theactual position of the second corner position differs with respect tothe estimated position depending on the orientation of the far-sideobstacle. Specifically, comparing a case where the parked vehicle 62 asthe far-side obstacle is parked with its front facing forward, i.e.,parked in a direction that is perpendicular to the direction in whichthe own vehicle 40 moves toward the parking space 50, and a case whereit is obliquely parked in such a manner that its front is inclinedtoward the own vehicle 40, in the latter, the estimated second cornerposition exists at a position that is further from the lateral passage51 as compared with the former. Therefore, in the latter case, theparking space 50 is recognized assuming that the actual second cornerposition is closer to the lateral passage 51 than the estimated secondcorner position. This makes it possible to recognize the parking space50 more accurately.

In the above embodiments, a case was explained where the own vehicle 40is parked parallelly in the parking space 50 sandwiched between twoparallelly parked vehicles 61 and 62. However, the configuration of thepresent disclosure may be applied to the case where the own vehicle 40is serially parked in a parking space sandwiched between two seriallyparked vehicles. As with the former case, the parking space can berecognized earlier while the own vehicle 40 is heading toward theparking space, and serial parking in a single attempt can be realized.Further, the parking place is not particularly limited, and it may be anoutdoor parking lot, an indoor parking lot, a garage, or the like.

In the above embodiments, a case is explained where techniques of thepresent disclosure is applied to a system that performs automaticparking control for parking the own vehicle 40 automatically by forwardparking in the parking space 50 recognized by the parking spacerecognition unit 12. However, it may be applied to a system in which theparking assistance device 10 guides the route for forward parking thevehicle in the parking space 50, and the driver performs the operationsfor parking.

In the above embodiment, the ranging sensor 22 is configured to includea sensor that transmits a probe wave and receives the reflected wavereflected by an obstacle, but the distance to the obstacle may bemeasured by the in-vehicle camera 21. The in-vehicle camera as theranging sensor may be a monocular camera or a stereo camera. When it isa monocular camera, the distance to the obstacle can be detectedaccording to the principle of deriving parallax from sequential images.When the distance to the obstacle is to be measured by the in-vehiclecamera, the function of capturing an image of the area in front of thevehicle and the function of measuring the distance to the obstacle maybe performed by a single camera.

The above-described constituent elements are conceptual and are notlimited to those of the above embodiments. For example, the function ofone constituent element may be distributed to a plurality of constituentelements, or the functions of a plurality of constituent elements may beintegrated into one constituent element.

Although the present disclosure is described based on examples, itshould be understood that the present disclosure is not limited to theexamples and structures. The present disclosure encompasses variousmodifications and variations within the scope of equivalence. Inaddition, the scope of the present disclosure and the spirit includeother combinations and embodiments, only one component thereof, andother combinations and embodiments that are more than that or less thanthat.

The invention claimed is:
 1. A parking assistance device applied to avehicle equipped with a camera for capturing an image of an area infront of the vehicle and a ranging sensor, and configured to assistforward parking of the vehicle in a parking space, comprising: aposition estimation unit which, in a situation where the vehicle isadvancing toward the parking space in a lateral passage of the parkingspace, estimates, based on an image captured by the camera, a firstcorner position, which is a near-side corner position at a vehicleentrance part of the parking space, and a second corner position, whichis a far-side corner position at the vehicle entrance part, before thevehicle passes by the parking space; a space recognition unit whichrecognizes the parking space for forward parking based on the at leastone corner position estimated by the position estimation unit; and aposition detection unit which detects contour points of a near-sideobstacle located adjacent to the parking space on a near side of theparking space as viewed from the vehicle based on distance informationacquired by the ranging sensor, and detects a third corner position,which is a corner position of the near-side obstacle that is on the sideopposite to the parking space and on the side of the lateral passage,based on detection history of the contour points, wherein, the positionestimation unit estimates the second corner position by acquiring, fromthe image, position information of a far-side obstacle located adjacentto the parking space on a far side of the parking space as viewed fromthe vehicle, and estimates the first corner position according to thesymmetry of the near-side obstacle as a position obtained by, based onthe image, mirror-inverting the third corner position detected by theposition detection unit in a direction in which the vehicle advancestoward the parking space.
 2. The parking assistance device according toclaim 1, wherein, the parking assistance device performs automaticparking control for automatically parking the vehicle in the parkingspace by forward parking based on a recognition result of the parkingspace from the space recognition unit.
 3. A parking assistance methodapplied to a vehicle equipped with a camera for capturing an image of anarea in front of the vehicle and a ranging sensor, and configured toassist forward parking of the vehicle in a parking space, comprising:estimating, in a situation where the vehicle is advancing toward theparking space in a lateral passage of the parking space, and based on animage captured by the camera, a first corner position, which is anear-side corner position at a vehicle entrance part of the parkingspace, and a second corner position, which is a far-side corner positionat the vehicle entrance part, before the vehicle passes by the parkingspace; and recognizing the parking space for forward parking based onthe estimated at least one corner position, wherein, contour points of anear-side obstacle located adjacent to the parking space on a near sideof the parking space as viewed from the vehicle are detected based ondistance information acquired by the ranging sensor, and a third cornerposition, which is a corner position of the near-side obstacle that ison the side opposite to the parking space and on the side of the lateralpassage, is detected based on detection history of the contour points,the second corner position is estimated by acquiring, from the image,position information of a far-side obstacle located adjacent to theparking space on a far side of the parking space as viewed from thevehicle, and the first corner position is estimated according to thesymmetry of the near-side obstacle as a position obtained by, based onthe image, mirror-inverting the detected third corner position in adirection in which the vehicle advances toward the parking space.